This invention relates to a heat recuperator which is particularly useful in modern convection heating furnaces and, in particular, to a heat recuperator the major portion of which can be cast or rammed as a monolithic block of refractory material.
The rising cost of fossil fuels combined with the increased regulation of fossil fuel furnaces with respect to environmental conformity makes efficient use of such furnace systems imperative.
While heat exchangers for increasing the efficiency of fossil fuel furnaces have long been known, the known refractory structures are not suitable for economical fabrication or for use with modern convective combustion systems.
Typically, recuperators have heretofore been made by building up a plurality of interlocking ceramic pieces, each having tubular passages therein, in a manner defining mutually tranverse waste gas and combustion air passages. Typically the passages have a substantially uniform cross-section throughout their extent. Such built-up recuperators, however, are expensive to construct, thermally unhomogeneous, and unreliable because of leakage through numerous joints between adjacent pieces. The problem of leakage is particularly significant since modern convection heating furnaces have high combustion air entry pressures and discharge waste gases at substantially higher draft pressures than older furnaces.
As a consequence of the unreliability of built-up recuperators, industry has turned primarily to all-welded alloy steel recuperators. These recuperators, however, are very expensive because of the high cost of alloy materials and because skilled technicians are needed to perform the many separate welding operations required.